The majority of Americans eat less than the recommended amounts of fruits, vegetables, and whole grains. This includes preschool age children, which is a major concern since food preferences and eating habits developed in early childhood track into later childhood and early adulthood. In addition, diets rich in fruits, vegetables and whole grains protect against certain cancers, help maintain healthy weight, and reduce risks for diabetes and other chronic diseases. Thus, there is an urgent need for increasing consumption of fruits, vegetables, and whole grains in the diets of preschool children. With 73% of US children ages 3-5 in regular non-parental care, childcare is a very important setting for encouraging parents to increase young children's opportunities to eat and enjoy fruits, vegetables and whole grains; despite this opportunity, few studies have been conducted in childcare settings. The primary aim of this proposal is to evaluate Lunch is in the Bag, a behaviorally-based, multilevel intervention to increase the availability of fruits, vegetables, and whole grains in sack lunches in childcare centers. The intervention includes 5 weekly parent handouts, along with center- based parent and child activities to reinforce concepts in the handouts, followed by a booster activity three months after the initial intervention. Outcome measures include changes in (1) the amounts of fruits, vegetables, whole grains, chips, and sweets packed in the sack lunches; (2) the amounts of these foods consumed by the children; (3) parent knowledge, norms and intention; (4) teacher support and awareness; and (5) center environment to support a healthy diet. Secondary aims are to determine the mediating factors for the intervention. Additional aims include the evaluation of factors affecting implementation and adaption. Childcare centers (n=40) that require parents to send sack lunches from home will be randomized to intervention and control groups. Families (n=800) will be enrolled as parent-child dyads comprised of the primary lunch packer and one 3 to 5 year old child per family. Outcome measures will be assessed at (1) baseline, (2) immediately after the five-week intervention (6 weeks), (3) 3 months later immediately before a booster activity (23 weeks), and (4) 5 weeks after the booster (28 weeks). Mediation analyses will be guided by the Theory of Planned Behavior (TPB) and Social Cognitive Theory (SCT), with particular attention to the reciprocal influences of the child's eating behavior and the parent's food packing behavior and perceptions of child food preferences. Qualitative and process data collection will be conducted throughout the intervention. Data from this study will enable us to determine the efficacy and feasibility of a parent-based intervention implemented through childcare centers to increase the availability of fruits, vegetables, and whole grains in diets of preschool children. The ultimate goal for this work is the development of new strategies for the promotion of healthy eating practices in children through childcare centers, which will decrease their risk of cancer and other chronic diseases later in life.